This study was funded by the Chief Scientist Program of Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (SIBS2008006), the Knowledge Innovation Program Project of the Chinese Academy of Sciences (KSCXI-YW-02, KSCX2-YWR-73, and KSCX2-YW-R-116), the Ministry of Science and Technology of China (973 Program, Grarn. 2006CB503902), and the Shanghai-Unilever Research Development Fund (CH-2006-0941).